For heating I use the Fermwrap
. A bit spendy, but I cut it into two pieces and wired the cut piece up with a spare power cord to make it essentially a 2 for 1 sale. It works really well, and for my fridge fermenter I stopped wrapping it around the fermenter. Instead I just hang it inside...works really well.
I've also seen folks use a reptile cage heater like this one
Some folks use a simple electric heating pad available from about any drug store.
If you want to go the DIY route, here
is a good write up for building a Fermwrap for cheap.